Apparatus for spinning cellulose esters dissolved in volatile solvents



APPARATUS FOR SPINNING CELLULOSE ESTERS DISSOLVED IN VOLATILE SOLVENTS Filed April 21, 1928 w slii.

Patented June 12, 1934 imaasos APPARATUS F OR SPINNING CELLULOSE ESTERS 'DISSOLVED IN VOLATILE SOL- VENTS Ugo Mancini, MilamItaly, assignor to :Ruth-Aldo Company Inc., New York, N. Y., a corporation of "New York Application April 21, 1928, SerialNo. 271,912 tIn'ltalyMarch 23, 1928 15 Claims.

1 rent of hot air which evaporates the volatile solvent, the filaments thereupon gradually losing their plasticity and solidifying.

It is also knownto be a matter of prime importance, as regards economy of manufacture,

- that the whole of the vapors of the solvents should be recoverable: in the highest state of purity.

Atmospheres highly charged with vaporized solvents must be provided in the spinning ,cell,

at certain points. and especiallynear the ,spinof the solvent contained in the filament ,and

maintain the plasticity of the filaments as long as possible during their passage through the cell,

the object being to enable the thread to be subjected to agradual stretching without impairing its final properties of elasticity.

The proportion of vapors in the atmosphere surrounding the filamentsshould vary with the alterations in the rate ofspinning, the ,denier of '30 the thread, the diameter and number of the orifices in the spinning nozzle and the concentra-v tion of the cellulose-ester solution employed; ,so that the optimum concentration can be obtained for each group of values of said variables.

Themethods employed for recovering the volatile solvents are:-

1. Recovery by condensation through-cooling.

This is practicable only in the case of atmospheres comparativelyrich in vapors. The ,airis- 40 suing from the recuperator is still relatively laden with vaporsand must, therefore, be returned to the cycle of operations. inorder toprevent-loss of the vapors.

zhRecovery by. absorption. The absorption -is -effected by liquids which readilyidissolvethe solvent and canafterwards be easily and economically separated by fractional distillation. .This method is suitable for atmospheres with a low concentration of vaporized solvent.

3. "Recovery byabsorption in special solid substances (activated ,charcoals, silica, ,etc.) from which the solventsare afterwards expelled by heating or'by displacement withsteam, the mixture of solventand watenof ,condensationbeing --then distilled. This method also "is suitable for =20 ning nozzle, in order to retard theevaporation' solutions.

atmospheres with a low concentration of volatile vapors.

.In the industrial .process of spinning with multiple cells and with different solutions of esters, it is necessary, (in order to obtain filaments .displaying good characteristics, of difierent denier, and produced at diiferent spinning velocities) to regulate the admission of air into the cells, the concentration of vaporized solvents inthe interior of the cells, and the temperature of the air at the point of entry and in the interior of the cells.

All these ,factors are so closely interrelated that no system of spinning which does not permit of their individual regulation can attain industrial importance.

The present invention provides a system of heating and circulating the air, which enables the various factors to be regulated and at the same time renders possible the recovery of the volatile vapors almost in their entirety.

The system comprises or may comprise a closed'heating circuit to be traversed by the greater portion of the air circulating in the spinning cells, a branch condensing circuit, a subebranch leading from the delivery side of the condenser to a vapor absorption or recovery plant, and control means for said circuit, branch circuit and sub-branch.

Said closed circuit through the spinning cells may be constituted by a large collector for the vapor "laden air issuing from the cells, a fan for imparting motion to the air, a tubular heater in which the air is raised to a temperature of about 100 .C., and a distributor for distributing the heated air back to the cells such air passing, if desired,.through small special heaters, one for each cell, whose function is to make good any'loss in temperature and to enable the air to be admitted into the several cells at the desired temperature.

'Said branch circuit,.which communicates with the closed circuit in advance of the tubular heater, may include a condenser cooled to the desired temperature either by water or by cold By a suitable valve arrangement any desired proportion of the total air circulation can be ,diverted into the branch circuit so as to modi y, at will, the proportion of vaporized solvent contained in the air returned to the cells.

A sub-branch .for drawing off air from the branch circuit, at a point beyond the condenser, may communicate with a suction device passing said air into the absorption plant. .By regulating the amount of air drawn off by the subbranch, it is possible to fix, at will, the amount of air which may pass from the atmosphere into the cells by way of the discharge orifices for the threads.

Pipes may connect the absorption plant with suction slots located near the ports through which access is gained to the cells, so that when said ports are opened the suction slots are uncovered and solvent vapor which would otherwise escape through the opened ports are led to the absorption plant.

In addition to the main heater and the special heaters aforesaid, a heating jacket may be provided round the upper part of each cell, for the purpose of restoring the temperature of the air which has traversed the first part of the cell.

By means of the system described it is possible to regulate:-

(a) The amount of air in circulation (by controlling the suction fan):

(2)) The air temperature (by regulating the main and the secondary heaters) (c) The proportion of vaporized solvent in the air at its entry into the cells, and therefore at its escape therefrom.

At the same time the recovery of the greater portion of the solvent is obtained by condensing the vapors.

A typical embodiment of the invention is illustrated diagrammatically by the single figure of the accompanying drawing to which reference will now be made.

A denotes one of a series of cells constituting a spinning machine or group of such machines; B and C are respectively the inlet for the hot air to the cell and the outlet therefrom for the vapor laden air.

E and F are two butterfiy valves, which act simultaneously and serve to shut ofi' communication between the cell and the circulating system when the cell is to be opened for any reason.

G is a tubular collector receiving the saturated air aspirated by the different cells. This tube is of large section because the loss of head sustained in passing therethrough has no appreciable influence on the negative pressures at the cell outlets C. Said tube is in direct and immediate communication with a suction fan H, which is provided with a by-pass and valve H to regulate the effective draught of the fan. The vapor laden air delivered by the fan passes, in part, directly into a heater K, and in part into a condenser I included in a branch circuit. The amount of air passed through the condenser can be regulated at will by manipulating valves M, L and N. This air, after parting with a large proportion of the vaporized solvent in the condenser, is returned to the air in the primary circuit, in order to pass through a main heater K in that circuit. On issuing from the latter, the air is admitted into the distributor G whence it passes to separate heaters U and, from these, returns to the different cells by way of the valves F.

P is a controlled sub-branch for drawing off air from the branch circuit on the delivery side of the condenser I, and is in communication with a suction device and an absorption vessel W. To this vessel W are connected pipes Z and Y, which carry off any vapor-laden air which may escape from the port openings of the cells when the ports D are opened.

Equal distribution of hot air into each cell is effected by means of orifice plates T of suitable dimensions attached to the separate heaters U.

T and T are differential pressure gauges for measuring the air current to enable the determination of the total air circulation or the proportion of air obliged to pass through the condenser. S is a gauge for ascertaining the amount of air drawn off from the circuit, to which corresponds a similar volume of air entering the cells through the discharge orifices for the threads.

The solvent condensed in the condenser I is passed by way of a siphon Q through a meter R which records the amount of solvent recovered by condensation.

V is an auxiliary heater, one for each cell, traversed by water at a temperature of about C.

Having now fully described my said invention and the manner in which the same is to be performed, I declare that what I claim as my invention and desire to secure by Letters Patent is:

1. In an apparatus including a cell for spinning cellulose esters dissolved in volatile solvents, a normally open circuit through which vaporladen air may be withdrawn from said cell and returned thereto, a branch-condensing circuit, said branch-condensing circuit being normally open, whereby vapor-laden air may simultaneously pass through both circuits, means in said branch-condensing circuit for regulating the amount of vapor-laden air circulating therethrough, a vapor recovery plant, and a branch leading from the delivery side of the branchcondensing circuit to the vapor recovery plant.

2. In an apparatus including any desired number of cells for spinning cellulose esters dissolved in volatile solvents, a normally open circuit through which vapor-laden air may be withdrawn from said cells and returned thereto, including a collector for the vapor-laden air issuing from the cells and a distributor for distributing the air back to the cells, means for imparting motion to the air in said circuit, a heater for raising the temperature of the air as it passes through a part of said circuit, a branch-condensing circuit, said branch-condensing circuit being normally open, whereby vapor-laden air may simultaneously pass through both circuits, means in said branch-condensing circuit for regulating the amount of vapor-laden air circulating therethrough, a vapor recovery plant and a branch leading from the delivery side of the branch-condensing circuit to the vapor recovery plant.

3. In apparatus including any desired number of cells for spinning cellulose esters dissolved in volatile solvents, an air circulating system comprising a closed heating circuit in communication with the cells, a branch condensing circuit, a sub-branch leading from the delivery side of the branch condensing circuit to vapor recovery plant, pipes connecting the port orifices of the cells with the sub-branch, and control means for said heating circuit, condensing circuit and subbranch for the purpose specified.

4. In apparatus for spinning cellulose esters dissolved in volatile solvents; a plurality of spinning cells, a closed heating circuit in communication with the cells, a branch condensing circuit both ends of which are in connection with said heating circuit, a vapor recovery means, a subbranch leading from the delivery side of the branch condensing circuit to said vapor recovery means, and means for independently controlling said heating circuit, the vapor content of the air in the condensing circuit, and the sub-branch.

5. In apparatus for spinning cellulose esters dissolved in volatile solvents; a plurality of spinning cells, an air circulating system comprising a closed heating circuit in communication with the cells, a branch condensing circuit both ends of which are in connection with the heating circuit in advance of the heating element, a sub branch leading from the delivery side of the branch condensing circuit to a vapor recovery plant, and independent control means for said heating circuit, for the branch condensing circuit and for the sub-branch.

6. In apparatus including any desired number of cells for spinning cellulose esters dissolved in volatile solvents; an air circulating system comprising a closed circuit through the cells, a fan included in the closed circuit, heating means in the closed circuit, a branch condensing circuit both ends of which communicate with the closed circuit in advance of the heating means therein, a sub-branch leading from the delivery side of the branch condensing circuit to a vapor recovery plant; and separate control means for said closed circuit, for the branch condensing circuit, and for the sub-branch.

7. In apparatus including any desired number of cells for spinning cellulose esters dissolved in volatile solvents; an air circulating system comprising a closed circuit including the cells, a fan included in the closed circuit, a valve-controlled by-pass for the fan, heating means in the closed circuit, a branch condensing circuit both ends of which communicate with the said closed circuit in advance of the heating means therein, a vapor recovery plant, a sub-branch leading from the delivery side of the branch condensing circuit to said vapor recovery plant; and separate control means for said closed circuit, for the vapor content of the air in the condensing circuit, and for the sub-branch.

8. In apparatus for spinning cellulose esters dissolved in volatile solvents; a spinning cell, means for continuously withdrawing air laden with solvent vapors, means for separating the solvent vapors from such air, means for heating the separated air, and means for returning such air to the cell; all operating in a closed circuit.

9. In apparatus for spinning cellulose esters dissolved in volatile solvents; a spinning cell, means for continuously withdrawing air laden with solvent vapors, means for separating the solvent vapors from such air, means for heating the separated air, and means for returning such air to the cell, all operating in a closed circuit; and means whereby the proportion of vaporized solvent present in the atmosphere in the cell can be regulated.

10. In apparatus for spinning cellulose esters dissolved in volatile solvents; a spinning cell, means for continuously withdrawing air ladenwith solvent vapors, means for separating the solvent vapors from such air, means for heating the separated air, and means for returning such air to the cell, all operating in a closed circuit; and separate means whereby the ratio of air free from solvent vapor, of air not free from solvent vapors, and of the proportion of vaporized solvent present in the atmosphere of the cell, can be regulated.

11. In apparatus including any desired number of cells for spinning cellulose esters dissolved in volatile solvents; an air circulating system comprising a closed circuit including the cells, a fan included in said closed circuit, heating means in said closed circuit, and a Vapor condensing means exterior to said circuit but having its inlet and outlet connected with the said closed circuit between the cells and the heating means; and separate control means for said closed circuit, and the condensing means.

12. In apparatus including any desired number of cells for spinning cellulose esters dissolved in volatile solvents; an air circulating system comprising a closed circuit including the cells, a fan included in said closed circuit, heating means in said closed circuit, a vapor condensing means exterior to said circuit but having its inlet and outlet connected with the said closed circuit between the cells and the heating means; an absorption vessel, a connection between the delivery side of the condensing means and said absorption vessel; and separate control means for said closed circuit, the condensing circuit, and the connection with the absorption vessel.

13; A process for controlling the evaporation of solvents in spinning rayon which comprises continuous removal from the spinning cell of air carrying solvent vapor, passing said air through a heater and back to the cell and passing a predetermined percentage of said solvent laden air through a solvent recovery apparatus before passing to the heater.

14. A process as set forth in claim 13 in which means is provided for regulating the percentage of solvent laden air passing through the solvent recovery apparatus.

15. Apparatus for dry spinning rayon, including a spinning cell having an opening for access to the interior thereof, means normally closing said opening and a system connected to said cell through which air carrying solvent vapor is passed from the cell, and means for withdrawing solvent vapor from said opening and discharging it into said system adapted for operation when said opening is uncovered.

UGO MANCINI. 

